The invention relates to communications systems generally and, more particularly, the invention relates to an MPEG-like information distribution system providing enhanced information quality and security.
In some communications systems the data to be transmitted is compressed so that the available bandwidth is used more efficiently. For example, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1 refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is incorporated herein by reference. A compressed digital video system is described in the Advanced Television Systems Committee (ATSC) digital television standard document A/53, and is incorporated herein by reference.
The above-referenced standards describe data processing and manipulation techniques that are well suited to the compression and delivery of video, audio and other information using fixed or variable length digital communications systems. In particular, the above-referenced standards, and other xe2x80x9cMPEG-likexe2x80x9d standards and techniques, compress, illustratively, video information using intra-frame coding techniques (such as run-length coding, Huffman coding and the like) and inter-frame coding techniques (such as forward and backward predictive coding, motion compensation and the like). Specifically, in the case of video processing systems, MPEG and MPEG-like video processing systems are characterized by prediction-based compression encoding of video frames with or without intra- and/or inter-frame motion compensation encoding.
In the context of digital video processing and digital image processing, information such as pixel intensity and pixel color depth of a digital image is encoded as a binary integer between 0 and 2nxe2x88x921. For example, film makers and television studios typically utilize video information having 10-bit pixel intensity and pixel color depth, which produces luminance and chrominance values of between zero and 1023. While the 10-bit dynamic range of the video information may be preserved on film and in the studio, the above-referenced standards (and communication systems adapted to those standards) typically utilize a dynamic range of only 8-bits. Thus, the quality of a film, video or other information source provided to an ultimate information consumer is degraded by dynamic range constraints of the information encoding methodologies and communication networks used to provide such information to a consumer.
Therefore, it is seen to be desirable to provide a method and apparatus to preserve the dynamic range of film, video and other forms of relatively high dynamic range information that are encoded and transported according to relatively low dynamic range techniques. Moreover, it is seen to be desirable to provide such dynamic range preservation while utilizing economies of scale inherent to these relatively low dynamic range techniques, such as the above-referenced MPEG-like standards and techniques.
The invention provides a low cost method and apparatus for compressing, multiplexing and, in optional embodiments, encrypting, transporting, decrypting, decompressing and presenting high quality video information in a manner that substantially preserves the fidelity of the video information. In addition, standard quality circuits are used in a manner implementing, e.g., a high quality compression apparatus suitable for use in the invention. In optionally embodiments, pre-processing techniques are used to extend the apparent dynamic range of the standard compression, transport and decompression systems utilized by the invention.
Specifically, an apparatus according to the invention is suitable for use in a system for distributing a video information signal comprising a plurality of full dynamic range components and comprises: a compression encoder, for compression encoding the video information signal in a manner substantially retaining the full dynamic range of the full dynamic range components, the compression encoder comprising at least two standard encoders, each of the standard encoders being responsive to up to three component video signals, each of the standard compression encoders tending to substantially preserve a dynamic range and spatial resolution of only one component of the video signal, each of the standard compression encoders providing a compressed output video signal; and a multiplexer, for multiplexing the compressed output video signals of the two or more standard compression encoders to produce a multiplexed information stream.
In another embodiment of the invention, each of three standard YUV-type MPEG encoders (e.g., 4:2:0 or 4:2:2) is used to encode a respective one of three component video signals utilizing only a luminance encoding portion of the encoder. A standard transport system delivers the three encoded component video signals to three standard YUV-type MPEG decoders (e.g., 4:2:0 or 4:2:2), which are each used to decode a respective encoded component video signal utilizing a luminance decoding portion of the decoder.